1. Field of the Invention
The present invention relates to a setting tool for driving fastening elements in constructional components and driven by expanding gases and including a housing, and a setting mechanism located in the housing for driving the fastening element in a constructional component and including a combustion chamber, a piston guide adjoining the combustion chamber, a bolt guide for the fastening element and adjoining the piston guide in a setting direction, and a drive piston displaceable in the piston guide for driving the fastening element received in the bolt guide and driven by expanding gases generated in the combustion chamber. The drive piston has a piston head and a piston body connectable with the piston head along an interface, with the piston head and the piston body having, respectively, in an interface region, at least one stop surface and at least one counter-stop surface.
2. Description of the Prior Art
In the setting tools driven by expanding gases of the type discussed above, the piston head defines a piston area.
In setting tools with a comparatively small drive pressure of the expanding gases, the piston area should be significantly increased in order to provide a sufficiently large driving force. In order to prevent the increase of weight by the same amount, the piston body and the piston plate or head are formed as separate parts of different materials and which are then assembled. The piston body is formed, preferably, of a high-strength material because it directly contacts the set-in fastening element and should transmit, at a small diameter, which is substantially smaller than the head diameter, large forces.
U.S. Pat. No. 5,860,580 discloses a setting tool of the type described above and having a two-part piston in which a threaded connection provides for a fixed connection of the piston head with the piston body. The centering of the piston head with the piston body is carried out by the thread, whereas the transverse alignment of the piston head with the piston body is carried out by opposite flat or planar surfaces of the piston head and the piston body.
The drawbacks of such a piston consist in that the thread adversely influences the orthogonality between the piston head and the piston body because it is subjected to distortion upon hardening of the piston body by heat treatment. The orthogonality between the piston head and the piston body is necessary for retaining the piston in a proper setting position. The manufacturing of such piston is very expensive.
Accordingly, an object of the invention to provide a setting tool driven by expanding gases in which the orthogonality between the piston body and the piston head is insured.
Another object of the present invention is to provide a setting tool with which the manufacturing of the drive piston and, thus, of the setting tool is cost-effective.